How anaemia blocks anaemia

25th March 2008

An inherited anaemic blood disorder offers paradoxical protection to children who get a severe attack of malaria, according to a recent study into the phenomenon.

A report published in the online open access journal PLoS Medicine looks at how alpha thalassaemia, which is common in many areas of the world where malaria is endemic, actually protects children from a far more severe form of anaemia caused by malaria.

People with the condition have abnormally high levels of red blood cells rather than lower levels, but their red blood cells are smaller than normal.

The protective link between the two forms of anaemia was first made in the 1990s, but the latest research sheds more light on exactly how the protective factor operates.

Children with homozygous alpha thalassaemia — are 60% less likely to develop severe malarial anaemia (SMA) when suffering from malaria.

An international team of researchers looked at data from studies of more than 800 children from Papua New Guinea, which has a high incidence of alpha thalassaemia -- around 70%.

Typically, a child suffering from malaria loses between 30 and 40% of their red blood cells. The alpha thalassaemia children, however, are at an advantage, because of the high number of red blood cells they start out with.

The study's authors concluded that their pool of haemoglobin remains at a safe level despite losing a large number of red blood cells during a malaria attack.

Co-author Karen Day, chair of the Department of Medical Parasitology at the New York University Medical Center, said SMA contributes significantly to the morbidity and mortality associated with malaria.

Day said SMA is defined as having less than 50 grams of haemoglobin per litre of blood. But Alpha thalassaemia paradoxically may keep children above that danger level in the face of a malarial attack, she added.

Co-author Stephen Allen, reader in paediatrics at Swansea University said the study highlighted the importance of research into the relationship between inherited blood cell abnormalities and malaria.

He called for further research to assess how protection against anaemia might have an impact on other severe manifestations of malaria, and into any other protective mechanisms that occurred in alpha thalassaemic children.